What amount of gasoline was consumed by the engine of a car that traveled 300 km at an average speed

What amount of gasoline was consumed by the engine of a car that traveled 300 km at an average speed of 100 km / h, if the mechanical power of the engine is 46 kW? Motor efficiency is 36%

Initial data: S (vehicle path) = 300 km (300 * 10 ^ 3 m); V (average speed) = 100 km / h (27.78 m / s); N (motor mechanical power) = 46 kW (46 * 10 ^ 3 W); η (motor efficiency) = 36% (0.36).

Reference values: q (specific heat of combustion of gasoline) = 4.6 * 10 ^ 7 J / kg.

We express the mass of gasoline consumed by the engine from the formula: η = Ap / Q = N * t / (q * m) = N * S / (q * m * V), whence m = N * S / (η * q * V) …

Calculation: m = 46 * 10 ^ 3 * 300 * 10 ^ 3 / (0.36 * 4.6 * 10 ^ 7 * 27.78) = 30 kg.